Mold apparatus for high pressure casting

ABSTRACT

A mold apparatus for high pressure casting includes an upper mold having an internal space filled with a molten metal and a core pin elevating groove at an inner wall of the upper mold. A lower mold is disposed at a lower part of the upper mold and fixed with an insert. A core pin portion is elevatably installed in the core pin elevating groove to be elevated depending on a filling pressure of the molten metal filled in the internal space.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of priority to Korean PatentApplication No. 10-2015-0170023, filed on Dec. 1, 2015, the entirecontent of which is incorporated herein for all purposes by thisreference.

TECHNICAL FIELD

The present disclosure relates to a mold apparatus for high pressurecasting, and more particularly, to a mold apparatus for high pressurecasting having improved durability and quality by preventing an insertportion coupled to a core pin from being exposed to outside when acasting into which an insert is inserted is manufactured by highpressure casting.

BACKGROUND

Generally, a core pin is used to cast a casting into which an, insert isinserted or a casting having a hollow portion. As a representativeexample of the core pin, there is a resin-coated sand core used for lowpressure and gravity casting.

On the other hand, high pressure casting has a casting production cycletime shorter than that of other casting methods, and therefore, issuitable for mass production of the casting. As a core for the highpressure casting, instead of using the sand core whose strength is weak,a mold core pin which can bear a high pressure is used.

FIG. 1 is a photograph showing an existing insert exposed to an outsideof a core pin insertion portion, after a casting is taken out.

As illustrated in FIG. 1, when the casting is casted under a highpressure by supporting the insert using the above-mentioned core pin, apart of the insert fixed and supported by the core pin after the castingis taken out is not filled with molten metal, and therefore, may beexposed to outside.

When the insert is exposed to the outside, the exposed part may becorroded, or water or oil may be leaked to the outside.

Therefore, a method for inserting a cap made of a silicon or rubbermaterial into the insert, which is exposed to the outside due to thecore pin used to fix the existing insert to protect the exposed part,has been used.

However, the method may degrade durability and quality of the casting,that is, a finished product in the end and increase man hours due to apost-processing operation such as cap insertion to increasemanufacturing costs.

SUMMARY

An object of the present disclosure is to provide a mold apparatus forhigh pressure casting capable of preventing exposure of an insert due tothe fact that a core pin insertion portion is not filled with a moltenmetal when a casting into which the insert is inserted is manufacturedby high pressure casting.

According to an exemplary embodiment in the preset disclosure, a moldapparatus for high pressure casting includes an upper mold having aninternal space filled with a molten metal and a core pin elevatinggroove at an inner wall of the upper mold; a lower mold disposed at alower part of the upper mold and fixed with an insert; and a core pinportion elevatably disposed in the core pin elevating groove to beelevated depending on a filling pressure of the molten metal filled inthe internal space.

The core pin portion may include: a fixed bar having one side insertedinto and fixed to the core pin elevating groove; a core pin disposed atanother side of the fixed bar to be elevated along an innercircumferential surface of the core pin elevating groove; and a springhaving one side fixed to the core pin and another side fixed to an innercircumferential surface of a ceiling of the core pin elevating groove toprovide an elastic force to the core pin.

The spring may satisfy a spring constant value calculated by thefollowing Equation:

spring constant=casting pressure x core pin area/core pin movingdistance.

The spring may be made of any one of a spring steel, an oil-temperedwire for a valve spring, a hard drawn steel wire, a piano wire, and astainless steel wire that have a lateral modulus of 7000 to 8000kgf/mm².

The molten metal filled in the internal space may be filled at apressure of 10 to 1000 kg/cm².

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph showing an existing insert exposed to outside ofa core pin insertion portion after a casting is taken out.

FIG. 2 is a cross--sectional view illustrating a mold apparatus for highpressure casting according to an exemplary embodiment in the presentdisclosure.

FIG. 3 is a diagram for describing an operation of the mold apparatusfor high pressure casting according to the exemplary embodiment in thepresent disclosure.

FIG. 4 is a photograph showing a core pin according to an exemplaryembodiment in the present disclosure.

FIG. 5 is a photograph showing a core pin insertion portion after thecasting manufactured using the mold apparatus for high pressure castingaccording to the exemplary embodiment in the present disclosure is takenout.

DETAILED DESCRIPTION

Terminologies used herein are to mention only a specific exemplaryembodiment, and are not to limit the present disclosure. Singular formsused herein include plural forms as long as phrases do not clearlyindicate an opposite meaning. A term “ including” used in the presentspecification concretely indicates specific properties, regions, integernumbers, steps, operations, elements, and/or components, and is not toexclude presence or addition of other properties, regions, integernumbers, steps, operations, elements, components, and/or a groupthereof.

All terms including technical terms and scientific terms used hereinhave the same meaning as the meaning generally understood by thoseskilled in the art to which the present disclosure pertains unlessdefined otherwise. Terms defined in a generally used dictionary areadditionally interpreted as having the meaning matched to the relatedart document and the currently disclosed contents and are notinterpreted as ideal or formal meaning unless defined.

Hereinafter, a mold apparatus for high pressure casting according to anembodiment in the present disclosure will be described with reference tothe accompanying drawings.

Generally, to prevent an insert from being moved or deformed upon highpressure casting, a casting into which the insert is inserted is cast byfixing a total of three points, that is, two points of the insert fixedin a lower mold and one point thereof fixed in a core pin.

According to an exemplary embodiment in the present disclosure,durability and quality of the casting into which the manufactured insertis inserted may be improved by preventing the exposure of the insert tothe outside due to the fact that the part into which the core pin forfixing the insert is inserted is not filled with a molten metal.

FIG. 2 is a cross-sectional view illustrating a mold apparatus for highpressure casting according to an exemplary embodiment in the presentdisclosure, FIG. 3 is a diagram for describing an operation of a moldapparatus for high pressure casting according to an exemplary embodimentin the, present disclosure, and FIG. 4 is a photograph showing a corepin according to an exemplary embodiment in the present disclosure.

As illustrated in FIGS. 2 to 4, a mold apparatus for high pressurecasting includes an upper mold 100, a lower mold 200 to which an insert10 is fixed, and a core pin portion 300 elevatably installed in theupper mold 100 to selectively support the insert 10.

The upper mold 100 has an internal space 120 filled with a molten metaland includes at least one core pin elevating groove 110 so that aceiling thereof may have the core pin portion 300.

The core pin portion 300 is elevatably installed along an innercircumferential surface of the core pin portion 300 depending on whetherthe internal space 120 is filled with the molten metal, and thus,descends in a direction of the insert 10. Therefore, core pin portion300 may support the insert 10 when the molten metal is not filled, andthe core pin portion 300 moves up along an inner circumferential surfaceof the core pin elevating groove 110 by a pressure of the molten metalfilled in the internal space 120 when the molten metal is filled.

Therefore, a core pin insertion portion of the internal space 120 may bealso filled with the molten metal to prevent the insert 10 from beingexposed to outside.

The core pin portion 300 includes a fixed bar 310 having one side fixedto a ceiling of the core pin elevating groove 110, a core pin 320installed at another side of the fixed bar 310 to be elevated along thecore pin elevating groove 110, and a spring 330 providing an elasticforce to the core pin 320 to provide a support force for supporting theinsert 10.

The fixed bar 310 has a cylindrical shape and has one side fixed to aceiling of the core pin elevating groove 110 and another side providedwith a core pin separation preventing portion (not illustrated) toelevate the core pin 320 while preventing the core pin 320 from beingseparated and thus is coupled to the core pin 320.

The core pin 320 has a cylindrical shape having a diameter correspondingto that of the core pin elevating groove 110, in which the diameterranges from 0.7 to 3.4 cm.

The spring 330 has one side fixed to the ceiling of the core pinelevating groove 110 and another side fixed to the core pin 320 to pushthe core pin 320 in the direction of the insert 10, thereby providingsupport force for supplying the M insert 10. Hereinafter, a material ofthe spring 330 used in the present disclosure is shown.

TABLE 1 Division Kind of steel Remarks Spring steel SUP4/6/7/9/9A/10/Hot forming 11A Oil-tempered SWO, SWO-V, Cold forming wire for valveSWOSC-V spring Hard drawn SWB, SWC, SWP Cold forming steel wire, pianowire Stainless steel SUS302, SUS304, Cold forming wire SUS316/631

In one embodiment, a stainless steel wire having a lateral modulus (G)of 7000 to 8000 kgf/mm² is used as a material for the spring 330. Here,the spring 330 needs to be made of a material having excellent heatresistance to minimize deformation and damage of the spring 330 due to ahot molten metal.

Further, the spring 330 according to present disclosure is made of amaterial satisfying a spring constant (K) value calculated by thefollowing Equation (1)

spring constant (K)=casting pressure (P)×core pin area (A)/core pinmoving distance (S)   (1).

Generally, the diameter of the core pin 320 used upon the high pressurecasting ranges from 0.7 to 3.4 cm and the pressure of the molten metalfilled in the internal space 120, that is, a casting pressure (P) rangesfrom 10 to 1000 kg/cm².

Therefore, a force applied to the core pin 320 under the above castingpressure (P) is calculated by the following Equation (2):

force (N) applied to core pin=core pin area (A)×casting pressure (P)  (2).

Therefore, under the casting pressure (P) of 10 to 1000 kg/cm², theforce N applied to the core pin having a diameter of 0.7 to 3.4 cmranges from 0.385 to 9074.6 kg.

The core pin 320 needs to move up by at least 0.1 mm to prevent theinsert 10 in the core pin insertion portion from being exposed tooutside upon casting.

Therefore, the spring constant (K) value that may move the spring 330 by0.1 mm under the casting pressure P becomes a value obtained by dividingthe force (N) applied to the core pin by the core pin moving distance(S).

That is, the spring constant (K) value of the spring according to thepresent disclosure may satisfy 38.5 to 90,746 kg/mm.

Therefore, when the internal space 120 of the upper mold 100 is filledwith the molten metal, the core pin 320 moves up by at lea 0.1 mm by thepressure of the molten metal, that is, the casting pressure (P), bypreventing the exposure of the insert 10 to the outside due to the factthat the core pin insertion portion is not filled with the molten metal.Thus, durability, appearance quality, or the like of the manufacturedproduct are prevented from being degraded.

FIG. 5 is a photograph showing a core pin insertion portion after thecasting manufactured using the mold apparatus for high pressure castingaccording to the exemplary embodiment of the present invention is takenout.

As illustrated in FIG. 5, the core pin 320 moves up by at least 0.1 mmby the pressure of the molten metal upon the high pressure casting andthe internal space 120 is filled with the molten metal to prevent theinsert 10 from being exposed, thereby manufacturing a product havingexcellent surface quality and durability.

According to the exemplary embodiments in the present disclosure, thecore pin supporting the insert may naturally move back by the moltenmetal, and thus, the insert may be prevented from being exposed to theoutside, thereby improving durability and quality of the casting intowhich the insert is inserted.

Further, unnecessary processes such as a core pin removing process and acap inserting process may be omitted, thereby reducing savingmanufacturing costs and time.

Although exemplary embodiments have been described with reference to theaccompanying drawings, those skilled in the art will appreciate thatvarious modifications and alterations may be made without departing fromthe spirit or essential feature of the present invention.

Therefore, it should be understood that the above-mentioned embodimentsare not restrictive but are exemplary in all aspects. It is to beunderstood that the scope of the present invention will be defined bythe claims rather than the above-mentioned description and allmodifications and alternations derived from the claims and theirequivalents are included in the scope of the present invention.

What is claimed is:
 1. A mold apparatus for high pressure casting,comprising: an upper mold having an internal space filled with a moltenmetal and a core pin elevating groove at an inner wall of the uppermold; a lower mold disposed at a lower side of the upper mold and fixedwith an insert; and a core pin portion elevatably disposed in the corepin elevating groove to be elevated depending on a filling pressure ofthe molten metal filled in the internal space.
 2. The mold apparatus forhigh pressure casting of claim 1, wherein the core pin portion includes:a fixed bar having one side inserted into and fixed to the core pinelevating groove; a core pin disposed at another side of the fixed barto be elevated along an inner circumferential surface of the core pinelevating groove; and a spring having one side fixed to the core pin andanother side fixed to an inner circumferential surface of a ceiling ofthe core pin elevating groove to provide an elastic force to the corepin.
 3. The mold apparatus for high pressure casting of claim 2, whereinthe spring satisfies a spring constant value calculated by the followingEquation:spring constant=casting pressure×core pin area/core pin moving distance.4. The mold apparatus for high pressure casting of claim 3, wherein thespring is made of any one of a spring steel, an oil-tempered wire for avalve spring, a hard drawn steel wire, a piano wire, and a stainlesssteel wire that have a lateral modulus of 7000 to 8000 kgf/mm².
 5. Themold apparatus for high pressure casting of claim 1, wherein the moltenmetal filled in the internal space is filled at a pressure of 10 to 1000kg/cm².
 6. The mold apparatus high pressure casting of claim 1, whereinthe core pin portion selectively supports the insert.